A Functional Acknowledgment is a control message that confirms receipt and syntactic validity of transmitted EDI data. The receiving party sends a 997 back to the sender to report on the successful processing or rejection of one or more transaction sets within a functional group. The three core segments that structure this response are the AK1 (Functional Group Response Header), which identifies the functional group being acknowledged; the AK2 (Transaction Set Response Header), which reports on individual transaction sets and may loop to cover multiple documents; and the AK9 (Functional Group Response Trailer), which summarizes the overall acknowledgment results.

For example, when Acme Manufacturing submits a purchase order batch to Global Suppliers Inc. via EDI, Global Suppliers’ system receives the transmission and immediately generates a 997 Functional Acknowledgment. If all purchase orders in the batch pass syntax validation, Global Suppliers’ 997 indicates acceptance through the AK1 and AK9 segments. However, if one purchase order contains a data formatting error, the AK2 segment for that transaction set reports the rejection, potentially with AK3 (Data Segment Note) and AK4 (Data Element Note) segments detailing which field caused the problem. Acme Manufacturing receives this 997 and knows exactly which orders were accepted into their system and which require correction and resubmission.